Microbial Evolutionary Genomics, Institut Pasteur, 25-28 rue Dr. Roux, 75015, Paris, France.
CNRS, UMR3525, 25-28 rue Dr. Roux, 75015, Paris, France.
Nat Commun. 2017 Dec 12;8(1):2094. doi: 10.1038/s41467-017-02350-1.
Type II CRISPR-Cas systems introduce double-strand breaks into DNA of invading genetic material and use DNA fragments to acquire novel spacers during adaptation. These breaks can be the substrate of several DNA repair pathways, paving the way for interactions. We report that non-homologous end-joining (NHEJ) and type II-A CRISPR-Cas systems only co-occur once among 5563 fully sequenced prokaryotic genomes. We investigated experimentally the possible molecular interactions using the NHEJ pathway from Bacillus subtilis and the type II-A CRISPR-Cas systems from Streptococcus thermophilus and Streptococcus pyogenes. Our results suggest that the NHEJ system has no effect on CRISPR immunity. On the other hand, we provide evidence for the inhibition of NHEJ repair by the Csn2 protein. Our findings give insights on the complex interactions between CRISPR-Cas systems and repair mechanisms in bacteria, contributing to explain the scattered distribution of CRISPR-Cas systems in bacterial genome.
II 型 CRISPR-Cas 系统会在入侵的遗传物质的 DNA 中引入双链断裂，并在适应过程中利用 DNA 片段获取新的间隔区。这些断裂可以成为几种 DNA 修复途径的底物，为相互作用铺平道路。我们报告称，在 5563 个完全测序的原核基因组中，非同源末端连接（NHEJ）和 II 型-A CRISPR-Cas 系统仅出现过一次。我们使用枯草芽孢杆菌的 NHEJ 途径和嗜热链球菌和酿脓链球菌的 II 型-A CRISPR-Cas 系统进行了实验，以研究可能的分子相互作用。我们的结果表明，NHEJ 系统对 CRISPR 免疫没有影响。另一方面，我们提供了 Csn2 蛋白抑制 NHEJ 修复的证据。我们的研究结果深入了解了 CRISPR-Cas 系统与细菌中修复机制之间的复杂相互作用，有助于解释 CRISPR-Cas 系统在细菌基因组中的分散分布。
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